Importance Environmental heat and cold exposure (EHCE) remains the principal preventable cause of morbidity and mortality in children and adolescents globally. Objective To report EHCE-related burden and analyze its temporal trends among children and adolescents from 1990 to 2019. Design, Setting, and Participants This repeated cross-sectional study used data from the Global Burden of Disease Study 2019, which encompassed 204 countries and territories from 1990 to 2019. Children and adolescents aged 0 to 19 years were included in the study. Data analysis occurred from December 2023 to March 2024. Exposure EHCE in children and adolescents from January 1990 to December 2019. Main Outcomes and Measures The primary outcomes were cases and rates of EHCE incidence, prevalence, mortality, disability-adjusted life-years (DALYs), and average annual percentage changes (AAPCs). Global trends in these metrics were also analyzed by sex, age, and sociodemographic index (SDI), which is a comprehensive indicator of the socioeconomic status of a country or region. A linear regression model was used to calculate AAPCs and a joinpoint regression model was used to identify the years in which trends changed significantly. Results From 1990 to 2019, EHCE-related incidence, prevalence, mortality, and DALYs showed a downward trend globally. However, an upward trend in EHCE incidence and prevalence was detected between 2010 and 2019 (incidence AAPC, 1.46; 95% CI, 1.05-1.87; prevalence AAPC, 1.25; 95% CI, 1.01-1.50). Regionally, although EHCE-related incidence showed a decreasing trend in most regions from 1990 to 2019, there were still some regions with an increasing trend (Southern sub-Saharan Africa AAPC, 0.23; 95% CI, 0.01-0.44). In 2019, the mortality and DALYs of EHCE were higher among children and adolescents in countries with low SDI levels. Additionally, the burden of EHCE among children and adolescents varied according to sex and age. Conclusions and Relevance In this cross-sectional study, a global increase was observed in EHCE incidence and prevalence since 2010. Furthermore, children and adolescents in low-SDI regions, which bear the brunt of the climate crisis, were disproportionately impacted. This suggests that future responses to climate change crises should emphasize health equity, which implies that vulnerable populations, such as children and adolescents, should be given priority in the allocation of resources to address climate change.